The only free and comprehensive online etymological dictionary of the Spanish language
banda (2) f. (Noun) "band," "group"

16th cent. Re-borrowed from Old French bande 'id.,' itself borrowed from Old Occitan banda "regiment." Prior to the modern military sense, banda had been borrowed from Old French bande "group" in the 14th cent. to mean "flock," but was replaced by the later meaning. Borrowed from Gothic *bandwa "sign." A *bandwa referred to the banner or flag carried by a regiment, and was later applied to the regiment itself. From Proto-Germanic *bandwa- 'id.' Frorm Proto-Indo-European *bhonh2-tu̯éh2- 'id.' From the verb *bhó-n-h2-e- "to summon." From the root *bheh2- "to say" (see hablar).

Germanic: East Germanic: Gothic bandwo; North Germanic: Old Norse benda "to signal"
baño m. (Noun) "bath"

11th cent. From Vulgar Latin baneum 'id.,' from Latin balneum - a syncopated variant of the more conservative balineum - borrowed from Greek βαλανεῖον (balaneîon) "bath," "bathing room." A Pre-Greek substrate word.

Found in the villages of Baño, Galicia. In the feminine, found in the village name La Baña, used throughout Leon and Galicia. In the plural it is a common toponym throughout Spain, dating back to the public bath houses of Roman times. Also the origin of the Valencian surname Buñol and the Navarran surname Buñuel.

Romance: Western Vulgar Latin: Asturian bañu, Portuguese banho, Galician baño, Catalan bany, French bain, Italian bagno; Eastern Vulgar Latin: Romanian baie

"For a term for bathing in warm water, which is probably an Aegaean custom, we might expect a Pre-Greek origin." ~ Robert S. P. Beekes (2014).
bar m. (Noun) "bar," "tavern"

Borrowed from English bar, originally referring to a bar's countertop, itself borrowed from Old French bar "support." From Vulgar Latin *barra 'id.' The native word in Spanish is barra.
barca f. (Noun) "small ship"

12th cent. From Late Latin barca 'id.,' from Vulgar Latin *barica 'id.' From Latin baris "boat" with diminutive suffix -ica added. The word was borrowed from Greek βάρις (báris) "boat," (originally referring to Egyptian boats). A loanword from Coptic baare "small boat."

Also the origin of the surnames Barca and Barcas.

Romance: Western Vulgar Latin: Asturian barca, Portuguese barca, Galician barca, Catalan barca, French barque, Italian barca; Eastern Vulgar Latin: Romanian barcă
barco m. (Noun) "ship"

13th cent. From barca.

Also the origin of the surnames Barco, del Barco, Delbarco and Barcos.

Romance: Western Vulgar Latin: Asturian barcu, Portuguese barco

Cognates in Asturian barcu 'id.,' Galician and Portuguese barco 'id.' show that a tendency to use the word in the masculine happened at a late date in Iberian Vulgar Latin.
barra f. (Noun) "bar"

13th cent. From Vulgar Latin *barra 'id.' Of unknown origin.

The word is the origin behind Barra, the name of villages in Galicia and Asturias. Also the origin of the surname de la Barra.

Romance: Western Vulgar Latin: Asturian barra, Portuguese barra, Galician barra, Catalan barra, French barre, Italian barra; Eastern Vulgar Latin: Romanian bară; Extra-Comparanda: Basque barra
barrer (Verb) "to sweep"

13th cent. From Latin verrere 'id.' (Old Latin vorrere). From Proto-Italic *wors-e/o- 'id.' From Proto-Indo-European *u̯rs-e/o- "to wipe," "to harvest."

Romance: Western Vulgar Latin: Asturian barrer, Portuguese varrer, Galician varrer

Indo-European: Balto-Slavic: Russian Church Slavic vьrxu "to thresh;" Anatolian: Hittite u̯arš-i- "to harvest"
Barri m. (Toponym) "countryside," "forest," "corral"

Listed by Tibón (1988) as a common element in toponyms found around Basque territory, which he interpreted to mean not "new" but "sino "campo", "plantel", "bosque", "corral"." To that end, see also Barrio (2).
barrio (1) m. (Noun) "neighborhood"

10th cent. Borrowed from Andalusian Arabic barri "outskirts."

Not the origin of the surname Barrio.
Barrio (2) m. (Surname)

Of Basque origin, literally meaning "in the countryside." From Barri with the locative suffix -o. Erroneously taken to be from barrio (1) in the sense of "neighborhood" due to folk etymology.